A known reversible, lossless coding is a method of compressing information, such as a sound and an image. Besides, various types of compression coding methods have been proposed to deal with cases where a waveform is directly recorded in the form of a linear PCM signal (see Non-patent literature 1).
On the other hand, in audio transmission for long-distance telephone or VoIP, the logarithm approximation companding PCM (see Non-patent literature 2), in which the amplitude is expressed in logarithm approximation, is used instead of the linear PCM, in which the amplitude is expressed by a numerical value.    Non-patent literature 1: Mat Hans, “Lossless Compression of Digital Audio,” IEEE SIGNAL PROCESSING MAGAZINE, July 2001, pp. 21-32    Non-patent literature 2: ITU-T Recommendation G 711, “Pulse Code Modulation (PCM) of Voice Frequencies”